With a continuously growing population, it is becoming increasingly difficult to meet the world's energy needs as well as to kerb greenhouse gas emissions such as carbon dioxide emissions that are considered responsible for global warming phenomena. These concerns have triggered a drive towards more efficient electricity use in an attempt to reduce energy consumption.
One such area of concern is lighting applications, either in domestic or commercial settings. There is a clear trend towards the replacement of traditional incandescent light bulbs, which are notoriously power hungry, with more energy efficient replacements. Indeed, in many jurisdictions the production and retailing of incandescent light bulbs has been outlawed, thus forcing consumers to buy energy-efficient alternatives, e.g. when replacing incandescent light bulbs.
A particular promising alternative is provided by lighting devices including solid state lighting (SSL) elements, which can produce a unit luminous output at a fraction of the energy cost of incandescent light bulbs. An example of such a SSL element is a light emitting diode.
A problem hampering the penetration of the consumer markets by such lighting devices is that consumers are used to the appearance of incandescent lighting devices such as incandescent light bulbs, and as such expect the appearance of the replacement device to closely match this appearance. This is far from trivial when using SSL elements, as such elements can be considered to act as point light sources producing a directional luminous output. This is distinctly different to the glowing filament of an incandescent light source, which tend to produce an unidirectional luminous distribution.
Many design efforts of SSL element-based lighting devices have therefore focused on emulating the appearance of their incandescent equivalents. This however typically increases the cost of the SSL element-based alternative, which is also problematic given that even the simplest SSL element-based lighting devices are several times more expensive than their incandescent alternatives, and the high purchasing cost of these SSL element-based lighting devices also hampers significant market penetration.
For instance, U.S. Pat. No. 6,709,132 B2 discloses a LED bulb that emulates the appearance of a tungsten filament-based light bulb by including a flexible printed circuit board having a plurality of branches that are combined into a cage. The branches carry LEDs and each extend from a central aperture at a proximal end and have a hole at their distal ends, which the holes of respective branches are aligned in an overlay fashion such that a supporting rod is extended through the proximal central aperture and the distal overlaying holes when assembling the bulb. This however is a time-consuming process that is difficult to automate, as the distal apertures of the branches must be superimposed on each other to receive the supporting rod. This increases the cost of the LED bulb.
EP2314913A1 discloses a carrier for at least one light emitting unit comprises a mounting frame with mounting arms which are bent into a cage-like shape. However, such a mounting frame is formed before assembling into a cover. The outline of the cage-like mounting frame has to be smaller than the entry of the cover so that it can be inserted into the cover.